A research project funded by The Horse Trust hasmade a surprise discovery about the differences in tendon renewalbetween low and high strain equine tendons.

The research, which is being carried out by Helen Birch of the Institute of Orthopaedics & Musculoskeletal Science, University College London, aims to understand how tendons are renewed and how this process changes as horse’s age.

Dr Birch’s research, which was given £145,422 funding by The HorseTrust, is a three year programme, is due to complete in April2010 and aims to improve prevention and treatment of equine tendonitis, reducing suffering in horses. Tendonitis, which particularly affects racing horses, is one of the causes of lameness in horses.

Tendons are connective tissues that attach muscle to bone. Dr Birch’s research is focused on the tissue surrounding the sparse population of cells in tendon, known as the matrix, and the rate at which this tissue renews in horses. The mechanical properties of the tendon depend on the matrix, so understanding this tissue is key to understanding tendon injury.

Dr Birch compared matrix turnover in the superficial digital flexor tendon (SDFT) and the common digital extensor tendon (CDET). The SDFT is a high-strain, spring-like tendon that is prone to injury, while the CDET is low-strain, positional tendon that is less prone to injury.

Dr Birch originally hypothesised that the SDFT would have a higher turnover of matrix to repair the damage caused by the higher strain experienced by the tendon. However, she has been surprised to discover that it is the opposite way round – the high-strain SDFT has less ability to renew the matrix. Dr Birch does not yet know why this is, but hypothesises that SDFTs are protected from being turned over too much as this weakens the tendon.

Earlier research by Dr Birch showed how the tendon matrix in older horses show an accumulation of age-related products. She hypothesised that old cells will also synthesise less of the protein collagen which is responsible for providing the tendon with high strength, but early findings have found that cells in old tendons are still capable of producing new collagen.

Her research will now focus on investigating how the matrix is turned over and looking at the differences in the enzymatic process between CDET and SDFT and tendons of different ages. She hopes that a better understanding of the enzymatic process will enable researchers to understand why tendons degenerate and how to diagnose and prevent tendon injuries.

It is also claimed that this research into should also impact understanding of human tendons. For example, SDFT is similar to the Achilles tendon in humans.